JPS629196A - Finned heat exchanger - Google Patents

Abstract

PURPOSE:To restrain spaces between fins from being blockaded by frost upon frosting by a method wherein slit type cuttings are arranged on the surface of the fins at gaps in the step direction of heat transfer tubes and the widths of these cuttings are shortened stepwise from the inflow direction of air to the outflow direction of the same. CONSTITUTION:The width P1 of the slit type cutting 4 is long at the air inflow path of the fin 1, therefore, the local heat transfer area of the fin 1 is small and the amount of local heat exchange is low; as a result, the thickness of frost 3 at the air inflow part of the fin 1 becomes thin. The amount of local heat exchange of cooled and dehumidified air becomes higher gradually since the widths P2, P3, P4 of the slit type cuttings 5, 6, 7 are shortened stepwise with respect to the outflow direction of air and the local heat transfer area of the fin 1 is made large; accordingly, heat exchange is effected between the cooled and dehumidified air gradually and the frost 3 is formed while the frost 3 on the surface of the fin 1 forms the layer of frost of uniform thickness. Even in such case, the space between fins 1 will never be blockaded and ventilating path may be secured widely. Therefore, the number of times of defrosting operation is decreased and comfortable property upon room heating may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an outdoor finned heat exchanger such as a heat pump type air conditioner using air as a heat source.

BACKGROUND OF THE INVENTION Conventionally, heat exchangers used in air conditioners, etc. A finned heat exchanger having a configuration as shown in , b is used. That is, a large number of fins 1 are arranged in parallel at predetermined intervals to form a fin group, and heat exchanger tubes 2 are orthogonally crossed in multiple stages to this fin group. In particular, a heat exchanger with a siphon is constructed.

Furthermore, in order to improve the heat transfer effect between the fin 1 and a gaseous heat exchange fluid such as electricity, the fin 1 is formed into a wave shape with a constant wave pitch P5 on the surface of the fin 10. ing.

To explain the operation when such a finned heat exchanger is used during heating operation of a heat pump type air conditioner that uses air as a heat source, the outdoor finned heat exchanger functions as an evaporator, and the ambient air temperature When the temperature decreases, water vapor in the air adheres to the fin surface as frost 3 and forms a frost layer unless the evaporation temperature is below 0°C. When the space between the fins 1 is blocked by the frost 3, air cannot flow between the fins 1 and the heat exchange capacity decreases, and the heating capacity decreases.
A defrosting operation is performed to melt the frost 3 adhering to the surface of the fin 1.

Problems to be Solved by the Invention However, when the finned heat exchanger having the above-mentioned structure is used as an outdoor similar exchanger for a heat pump type air conditioner, etc. As shown in the detailed view of the fin air inflow end on line B-B', the turbulence of the main flow occurs from the fin 1'' inflow part, so more frost layer 3 is formed at the air inflow part of fin 1, and the frost layer 3 is formed in a short time. Since the space between the fins 1 was closed, the amount of air passing through the fins was reduced, and the amount of heat exchanged was significantly reduced in a short period of time.

Therefore, heating operation must be interrupted and defrosting operation must be performed frequently, which impairs the comfort during heating and also has poor energy efficiency.

The present invention eliminates the above-mentioned conventional drawbacks, suppresses the space obstruction of frost between the fins during frost formation, extends the time until the space between the fins is blocked by frost, and provides comfortable heating during heating. The present invention provides an excellent outdoor heat exchanger that improves performance and energy efficiency.

Means for Solving the Problems The finned heat exchanger of the present invention includes a group of fins arranged in parallel at regular intervals and through which air flows, and a stage of heat transfer tubes inserted at right angles to the group of fins. A large number of slit-like cutouts are arranged on the fin surface of the directional gap, and the width of the slit-like cutouts is made shorter in steps from the air inflow direction to the air outflow direction.

Function The present invention prevents the so-called development of the fin edges and the fin portions around the heat transfer tubes by the above-mentioned IIIt configuration, and uniformizes the formation of frost on the fin surface, thereby reducing the frost spots between the fins. It is possible to extend the blockage time due to clogging, reduce the number of defrosting operations, improve comfort during heating, and improve energy efficiency.

Example Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1a.

The explanation will be based on b.

FIG. 1a is a plan view of the fin shape of the finned heat exchanger of the present invention. In FIG. 1a, 1 is a fin, 2 is a heat exchanger tube, 3 is frost, 4.5, 6.7 are slit-shaped cutouts, and the slit-shaped cutouts 4.5.6, 7 width P
1. p2, P3, and P4 are configured to become shorter stepwise from the air inflow direction to the air outflow direction. Note that the arrow indicates the direction of air inflow.

FIG. 1 is a detailed sectional view of the air inflow end of the slit-like cutouts 4, 5, 6, 7 taken along the line A- in FIG. 1a in a frosted state.

The operation of the finned heat exchanger constructed as above will be explained based on FIGS. 1a and 1b.

Slit-shaped cutout portion 4.5 formed on one surface of the fin
．． Since the widths PI, p2, P3, and P4 of 6.7 are gradually shortened from the air inflow direction to the air outflow direction, the local heat exchange amount of the fin 1 is as follows.

It gradually increases from the direction of air inflow to the direction of air outflow.

Therefore, in the air inlet part of the fin 1, since the width pt of the slit-shaped cutout part 4 is long, the local heat transfer area of the fin 1 is small, the local heat exchange amount is low, and the surrounding area related to the amount of frost formation is The absolute humidity difference between the air and the saturated humid air corresponding to the heat exchanger heat transfer surface temperature becomes smaller, and as a result, the fin 1
The thickness of the frost 3 at the air inlet becomes thinner. The cooled and dehumidified air is then gradually shortened in widths P2, P3, and P4 of the slit-shaped cutouts 5.6.7 with respect to the outflow direction of the air, so that the local heat transfer area of the fin 1 is reduced. Since the amount of local heat exchange is increased, the amount of local heat exchange gradually increases, and frost 3 is formed as heat is exchanged with the gradually cooled and dehumidified air.

Therefore, the frost 3 on the surface of the fin 1 forms a frost layer with a uniform thickness, even if the same amount of frost layer is formed as in the conventional case.

A wide ventilation path can be ensured without being blocked between the fins 1. As a result, the increase in ventilation resistance is small, the amount of passing air is only slightly reduced, the amount of heat exchange is also reduced, the number of defrosting operations is reduced, and comfort during heating is improved, as well as energy efficiency. can be significantly improved.

In addition, in the slit-shaped cutouts 4.5.6.7, as shown in Figure 1, flow mixing occurs between adjacent fins, so the air side heat transfer coefficient improves and the null The fins of the present invention compensate for the decrease in the surface area of the fin 1 due to the slot-shaped cutout portions 4.5.6.7 and exchange heat better than those without the slot-shaped cutout portions 4.5.6.7. The heat exchanger has. Furthermore, in the area where the slit-shaped cutouts 4.5.6.7 are provided, molten water that melts during normal opening accumulates, and in the past, bridges due to molten water were likely to occur. Ta. When a bridge occurs at one end, it becomes a nucleus of frost during heating operation after defrosting, and the development of frost is accelerated.As a result, the heating operation time is shortened. however,
By providing the slit-shaped cut-out portion 4.5.6.7, it becomes difficult for water droplets to bridge, etc., and as a result, the heating operation time can be extended. has.

Effects of the Invention As is clear from the above explanation, the finned heat exchanger of the present invention has a group of fins arranged in parallel at regular intervals, through which air flows, and a group of fins inserted at right angles to the group of fins, so that the inside of the heat exchanger is A large number of slit-shaped cutouts are arranged on the fin surface of the gap in the direction of the heat transfer tubes, and the width of the slit-shaped cutouts is adjusted from the inflow direction to the outflow direction of the air. On the other hand, since the fins are made shorter in stages, the local heat exchange amount on the surface of the fin 1 gradually increases from the air inflow direction to the air outflow direction.
The frost on the fin surface forms a uniform layer of frost, and even if one layer of frost is formed, the space between the fins will not be blocked.
A wide ventilation path can be secured. As a result, there is little increase in ventilation resistance, only a slight decrease in the amount of air passing through, and a small decrease in the amount of heat exchange.This reduces the number of defrosting operations, improves comfort during heating, and significantly increases energy efficiency. can be improved.

In addition, since the flow mixes between adjacent fins through the slit-like cutouts, the air-side heat transfer coefficient of the fins improves, and the reduction in fin surface area due to the slit-like cutouts is compensated for.・Furthermore, since slit-shaped cutouts are formed on the fin surfaces located in the gaps in the direction of the heat transfer tube stage, the bridge of melted water during defrosting is improved. This has many practical effects, such as preventing the formation of frost nuclei during heating operation and extending the heating operation time.

[Brief Description of the Drawings] Fig. 1a is a plan view of the fin shape of a heat exchanger with fins showing an embodiment of the present invention;
A sectional view of the frosted state at the air inlet end along line A', Figure 2a is a plan view of the fin shape of a conventional finned heat exchanger;
The figure is a cross-sectional view of the air inflow end of the Mitsuin shown in FIG. 2 taken along line B-B' in a frosted state. 1...Fin, 2...Heat transfer tube, 3. Old...frost, 4.5.6.7...Slit-shaped cutout, Pl, P2, P3, P4... Width of the slit cutout 4.5.6.7. Name of agent: Patent attorney Toshio Nakao and one other person f.
fin

Claims (1)

[Claims] The fins in the gaps in the direction of the heat transfer tubes are composed of a group of fins arranged in parallel at regular intervals, through which air flows, and a group of heat transfer tubes inserted at right angles to the group of fins, through which fluid flows. A heat exchanger with fins in which a large number of slit-shaped cutouts are arranged on a surface, and the width of the slit-shaped cutouts is gradually shortened from the air inflow direction to the air outflow direction.